With development of communications technologies, data transmission between a terminal and a base station has become a focus of researches. In the prior art, terminals and base stations generally operate at a low frequency. For example, in a Long Term Evolution (LTE) technology, both terminals and base stations operate at a low frequency, that is, data is transmitted at a low frequency. During data communication, to assist a base station in improving transmission quality of low frequency downlink data, a terminal generally sends control information, for example, data retransmission request information, to the base station, and the base station responds to the data retransmission request and determines whether to perform data retransmission. In a manner of sending the control information, the terminal sends, at a low frequency to the base station, both the control information and data that needs to be transmitted.
For data transmission at a low frequency, a data rate is low, beam coverage is wide, and power consumption is low. For data transmission at a high frequency, a data rate is high, beam coverage is narrow, and power consumption is high. When a base station transmits data to a terminal, it is generally required that a higher data transmission rate is better. Therefore, it is put forward in the industry that a base station transmits data to a terminal at a high frequency when the base station transmits the data to the terminal, that is, the base station sends downlink data to the terminal at a high frequency. Because a data transmission rate at a high frequency is high, for an original method for sending control information by a terminal at a low frequency, a transmission time interval (TTI) is relatively long, that is, a feedback time is long. Therefore, the original method can no longer be applied to feed back control information that is used to improve transmission quality of high frequency downlink data. In addition, no method for feeding back control information in a timely manner is put forward in the industry in a process in which downlink data is transmitted at a high frequency.